Known in-plane modulus tests are typically conducted by a mechanical test through a tensile test machine which results in the destruction of the specimen. The specimen tested by such mechanical means is no longer reusable for further material processing. The difficulty in controlling couplant contamination on specimens and the lack of a practical dry contact ultrasonic technique limits the usefulness of known nondestructive tests of specimens, e.g. composites. Currently, most in-plane modulus testing of composites is conducted mechanically with a tensile test machine. To prepare for a mechanical test, a tensile test specimen is cut from the composite panel. Extensometers or strain gauges are installed on the specimen for a strain measurement. In addition, a stress measurement is also needed for the in-plane modulus evaluation by mechanical means. Accordingly, specimens tested by the mechanical method are no longer reusable for further material processing. In addition, the time required to perform in-plane modulus testing is relatively long.
Current state-of-the-art approaches often require immersion of the specimen into a water tank, although water immersion is not preferred and testing high-performance composites like ceramic composite materials (CMC) and metals during an ultrasonic measurement at elevated temperature. To achieve a couplant-free condition for an ultrasonic test, advanced tools such as lasers, electromagnetic acoustic transducers, and air coupled sensors have been reported, but poor sensitivity in ultrasonic signals and limitations to certain types of materials are typical drawbacks of these advanced methods. Current dry couplant materials which is available commercially does not provide sufficient sensitivity in transmitting ultrasound. No nondestructive evaluation (NDE) analysis can be performed using this material.